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pam


  1. pam.3.man
  2. pam.5.man
  3. pam.7.man
  4. pam.8.man


1. pam.3.man

Manpage of PAM

PAM

Section: Linux-PAM Manual (3)
Updated: 06/21/2011
Index Return to Main Contents
pam - Pluggable Authentication Modules Library  

Synopsis

#include <security/pam_appl.h>

#include <security/pam_modules.h>

#include <security/pam_ext.h>
 

DESCRIPTION

PAM is a system of libraries that handle the authentication tasks of applications (services) on the system. The library provides a stable general interface (Application Programming Interface - API) that privilege granting programs (such as login(1) and su(1)) defer to to perform standard authentication tasks.  

Initialization and Cleanup

The pam_start(3) function creates the PAM context and initiates the PAM transaction. It is the first of the PAM functions that needs to be called by an application. The transaction state is contained entirely within the structure identified by this handle, so it is possible to have multiple transactions in parallel. But it is not possible to use the same handle for different transactions, a new one is needed for every new context.

The pam_end(3) function terminates the PAM transaction and is the last function an application should call in the PAM context. Upon return the handle pamh is no longer valid and all memory associated with it will be invalid. It can be called at any time to terminate a PAM transaction.  

Authentication

The pam_authenticate(3) function is used to authenticate the user. The user is required to provide an authentication token depending upon the authentication service, usually this is a password, but could also be a finger print.

The pam_setcred(3) function manages the userscredentials.  

Account Management

The pam_acct_mgmt(3) function is used to determine if the users account is valid. It checks for authentication token and account expiration and verifies access restrictions. It is typically called after the user has been authenticated.  

Password Management

The pam_chauthtok(3) function is used to change the authentication token for a given user on request or because the token has expired.  

Session Management

The pam_open_session(3) function sets up a user session for a previously successful authenticated user. The session should later be terminated with a call to pam_close_session(3).  

Conversation

The PAM library uses an application-defined callback to allow a direct communication between a loaded module and the application. This callback is specified by the struct pam_conv passed to pam_start(3) at the start of the transaction. See pam_conv(3) for details.  

Data Objects

The pam_set_item(3) and pam_get_item(3) functions allows applications and PAM service modules to set and retrieve PAM informations.

The pam_get_user(3) function is the preferred method to obtain the username.

The pam_set_data(3) and pam_get_data(3) functions allows PAM service modules to set and retrieve free-form data from one invocation to another.  

Environment and Error Management

The pam_putenv(3), pam_getenv(3) and pam_getenvlist(3) functions are for maintaining a set of private environment variables.

The pam_strerror(3) function returns a pointer to a string describing the given PAM error code.  

RETURN VALUES

The following return codes are known by PAM:

PAM_ABORT

Critical error, immediate abort.

PAM_ACCT_EXPIRED

User account has expired.

PAM_AUTHINFO_UNAVAIL

Authentication service cannot retrieve authentication info.

PAM_AUTHTOK_DISABLE_AGING

Authentication token aging disabled.

PAM_AUTHTOK_ERR

Authentication token manipulation error.

PAM_AUTHTOK_EXPIRED

Authentication token expired.

PAM_AUTHTOK_LOCK_BUSY

Authentication token lock busy.

PAM_AUTHTOK_RECOVERY_ERR

Authentication information cannot be recovered.

PAM_AUTH_ERR

Authentication failure.

PAM_BUF_ERR

Memory buffer error.

PAM_CONV_ERR

Conversation failure.

PAM_CRED_ERR

Failure setting user credentials.

PAM_CRED_EXPIRED

User credentials expired.

PAM_CRED_INSUFFICIENT

Insufficient credentials to access authentication data.

PAM_CRED_UNAVAIL

Authentication service cannot retrieve user credentials.

PAM_IGNORE

The return value should be ignored by PAM dispatch.

PAM_MAXTRIES

Have exhausted maximum number of retries for service.

PAM_MODULE_UNKNOWN

Module is unknown.

PAM_NEW_AUTHTOK_REQD

Authentication token is no longer valid; new one required.

PAM_NO_MODULE_DATA

No module specific data is present.

PAM_OPEN_ERR

Failed to load module.

PAM_PERM_DENIED

Permission denied.

PAM_SERVICE_ERR

Error in service module.

PAM_SESSION_ERR

Cannot make/remove an entry for the specified session.

PAM_SUCCESS

Success.

PAM_SYMBOL_ERR

Symbol not found.

PAM_SYSTEM_ERR

System error.

PAM_TRY_AGAIN

Failed preliminary check by password service.

PAM_USER_UNKNOWN

User not known to the underlying authentication module.
 

SEE ALSO

pam_acct_mgmt(3), pam_authenticate(3), pam_chauthtok(3), pam_close_session(3), pam_conv(3), pam_end(3), pam_get_data(3), pam_getenv(3), pam_getenvlist(3), pam_get_item(3), pam_get_user(3), pam_open_session(3), pam_putenv(3), pam_set_data(3), pam_set_item(3), pam_setcred(3), pam_start(3), pam_strerror(3)  

NOTES

The libpam interfaces are only thread-safe if each thread within the multithreaded application uses its own PAM handle.


 

Index

Synopsis
DESCRIPTION
Initialization and Cleanup
Authentication
Account Management
Password Management
Session Management
Conversation
Data Objects
Environment and Error Management
RETURN VALUES
SEE ALSO
NOTES

This document was created by man2html using the manual pages.
Time: 17:31:57 GMT, October 23, 2013

2. pam.5.man

Manpage of pam

pam

Section: Netpbm pointer man pages (5)
Updated: Netpbm
Index Return to Main Contents

 

NAME

pam - see http://netpbm.sourceforge.net/doc/pam  

DESCRIPTION

pam is part of the Netpbm package. Netpbm documentation is kept in HTML format.

Please refer to <http://netpbm.sourceforge.net/doc//pam>.

If that doesn't work, also try <http://netpbm.sourceforge.net> and emailing Bryan Henderson, bryanh@giraffe-data.com.

Note that making the documentation available this way was a choice of the person who installed Netpbm on this system. It is also possible to install Netpbm such that you would simply see the documentation instead of the message you are reading now.


 

Index

NAME
DESCRIPTION

This document was created by man2html using the manual pages.
Time: 17:31:57 GMT, October 23, 2013

3. pam.7.man

Manpage of PAM

PAM

Section: Linux-PAM Manual (7)
Updated: 1997 Feb 9
Index Return to Main Contents
 

NAME

Linux-PAM - Pluggable Authentication Modules for Linux  

SYNOPSIS

/etc/pam.conf

 

DESCRIPTION

This manual is intended to offer a quick introduction to Linux-PAM. For more information the reader is directed to the Linux-PAM system administrators' guide.

Linux-PAM Is a system of libraries that handle the authentication tasks of applications (services) on the system. The library provides a stable general interface (Application Programming Interface - API) that privilege granting programs (such as login(1) and su(1)) defer to to perform standard authentication tasks.

The principal feature of the PAM approach is that the nature of the authentication is dynamically configurable. In other words, the system administrator is free to choose how individual service-providing applications will authenticate users. This dynamic configuration is set by the contents of the single Linux-PAM configuration file /etc/pam.conf. Alternatively, the configuration can be set by individual configuration files located in the /etc/pam.d/ directory. The presence of this directory will cause Linux-PAM to ignore /etc/pam.conf.

From the point of view of the system administrator, for whom this manual is provided, it is not of primary importance to understand the internal behavior of the Linux-PAM library. The important point to recognize is that the configuration file(s) define the connection between applications (services) and the pluggable authentication modules (PAMs) that perform the actual authentication tasks.

Linux-PAM separates the tasks of authentication into four independent management groups: account management; authentication management; password management; and session management. (We highlight the abbreviations used for these groups in the configuration file.)

Simply put, these groups take care of different aspects of a typical user's request for a restricted service:

account - provide account verification types of service: has the user's password expired?; is this user permitted access to the requested service?


authentication - establish the user is who they claim to be. Typically this is via some challenge-response request that the user must satisfy: if you are who you claim to be please enter your password. Not all authentications are of this type, there exist hardware based authentication schemes (such as the use of smart-cards and biometric devices), with suitable modules, these may be substituted seamlessly for more standard approaches to authentication - such is the flexibility of Linux-PAM.


password - this group's responsibility is the task of updating authentication mechanisms. Typically, such services are strongly coupled to those of the auth group. Some authentication mechanisms lend themselves well to being updated with such a function. Standard UN*X password-based access is the obvious example: please enter a replacement password.


session - this group of tasks cover things that should be done prior to a service being given and after it is withdrawn. Such tasks include the maintenance of audit trails and the mounting of the user's home directory. The session management group is important as it provides both an opening and closing hook for modules to affect the services available to a user.

 

The configuration file(s)

When a Linux-PAM aware privilege granting application is started, it activates its attachment to the PAM-API. This activation performs a number of tasks, the most important being the reading of the configuration file(s): /etc/pam.conf. Alternatively, this may be the contents of the /etc/pam.d/ directory.

These files list the PAMs that will do the authentication tasks required by this service, and the appropriate behavior of the PAM-API in the event that individual PAMs fail.

The syntax of the /etc/pam.conf configuration file is as follows. The file is made up of a list of rules, each rule is typically placed on a single line, but may be extended with an escaped end of line: `\<LF>'. Comments are preceded with `#' marks and extend to the next end of line.

The format of each rule is a space separated collection of tokens, the first three being case-insensitive:


service type control module-path module-arguments

The syntax of files contained in the /etc/pam.d/ directory, are identical except for the absence of any service field. In this case, the service is the name of the file in the /etc/pam.d/ directory. This filename must be in lower case.

An important feature of Linux-PAM, is that a number of rules may be stacked to combine the services of a number of PAMs for a given authentication task.

The service is typically the familiar name of the corresponding application: login and su are good examples. The service-name, other, is reserved for giving default rules. Only lines that mention the current service (or in the absence of such, the other entries) will be associated with the given service-application.

The type is the management group that the rule corresponds to. It is used to specify which of the management groups the subsequent module is to be associated with. Valid entries are: account; auth; password; and session. The meaning of each of these tokens was explained above.

The third field, control, indicates the behavior of the PAM-API should the module fail to succeed in its authentication task. Valid control values are: requisite - failure of such a PAM results in the immediate termination of the authentication process; required - failure of such a PAM will ultimately lead to the PAM-API returning failure but only after the remaining stacked modules (for this service and type) have been invoked; sufficient - success of such a module is enough to satisfy the authentication requirements of the stack of modules (if a prior required module has failed the success of this one is ignored); optional - the success or failure of this module is only important if it is the only module in the stack associated with this service+type.

module-path - this is the full filename of the PAM to be used by the application

module-arguments - these are a space separated list of tokens that can be used to modify the specific behavior of the given PAM. Such arguments will be documented for each individual module.

 

FILES

/etc/pam.conf - the configuration file
/etc/pam.d/ - the Linux-PAM configuration directory. If this directory is present, the /etc/pam.conf file is ignored.
/usr/lib/libpam.so.X - the dynamic library
/usr/lib/security/*.so - the PAMs

Note, to conform to the Linux File-system standard, the libraries and modules in your system may be located in /lib and /lib/security respectively.

 

ERRORS

Typically errors generated by the Linux-PAM system of libraries, will be written to syslog(3).

 

CONFORMING TO

DCE-RFC 86.0, October 1995.
Contains additional features, currently under consideration by the DCE-RFC committee.

 

BUGS

None known.

 

SEE ALSO

The three Linux-PAM Guides, for System administrators, module developers, and application developers.


 

Index

NAME
SYNOPSIS
DESCRIPTION
The configuration file(s)
FILES
ERRORS
CONFORMING TO
BUGS
SEE ALSO

This document was created by man2html using the manual pages.
Time: 17:31:57 GMT, October 23, 2013

4. pam.8.man

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